Abstract

Thermal management for high performance of miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and industry. Obtaining heat sink designs with uniform flow distribution is strongly desired. Mal-distribution in a standard straight microchannel heat sink has become a problematic issue in this research area. A cross-linking scheme, introduced in the channel core promises an appropriate solution to this problem due to flow sharing through the cross-links. In the present thesis, a number of experimental and numerical studies have been conducted to seek appropriate designs for microchannel heat sinks. The effects of cross links, introduced in the channel core of an array of parallel scaled microchannels, are investigated, by comparing the flow distribution and pressure drop in six different multi-channel configurations. A standard straight channel test section and five cross-linked test sections are experimentally investigated. All test sections have 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The flow distribution is monitored at four selected channels. The working mixture is air and water with superficial velocities ranging from 0.03 to 9.93 m/s, and 0.04 to 0.83 m/s, respectively. The results show that the cross-linked designs improve the flow distribution between channels compared to the standard straight channel configuration. Flow patterns obtained from flow visualization are presented in terms of fractional time function and a flow pattern map was developed. Compared with a single channel flow regime map, the expected intermittent flow regime is observed 84% to 90% of the time for the cross-linked designs, but only 65% to 80% of that for the straight channel design. A new cross-linked microchannel heat sink is proposed with the support of numerical investigations. The new design shows a significant improvement, up to 55%, on flow distribution when compared to the standard straight channel configuration without a penalty in pressure drop.